The research proposed in this study is to determine if secretory Immunoglobulin A (SIgA) and Dental caries are in any way correlated. One would expect that SIgA as an antibody would afford protection against microbes causing caries. We feel that our studies have at least made this hypothesis seem possible in that we find in ages 20-29 and 10-19 that SIgA and dental caries are inversely related. This is what one would expect if SIgA is affording protection. We also propose to increase the concentration of SIgA in hamsters, (our test system) to a particular antigen and then determine if the SIgA has a protective effect against this antigen. Preliminary studies appear to show an increase in SIgA concentration with immunization.